While the advantages of freezing and refrigerating foods is apparent, problems can and do arise if the electrical power, usually in the form of house current, fails to such freezers and refrigerators, or if for some reason the temperature within the freezer or refrigerator chamber rises above a prescribed level tending to thaw or unchill food. This problem is acutely prevalent in commercial freezing cabinets which are unattended for hours at a time, or in a person's home when the occupants are gone and for some reason the temperature rises above prescribed limits.
It is known to provide alarm circuits for such refrigerator and freezer cabinets which will sound or flash when the temperature rises above prescribed limits. Of course it is also possible that the temperature may fall to too low a level due to a malfunction in the refrigerant cycle, which situation should also be monitored. However, such situations generally require a self-contained power source, such as a battery, because one of the most prevalent reasons for the temperature rise is the loss of conventional house current. When this occurs, according to known systems, an alarm buzzer, gong, or light is caused to continuously sound or signal until an attendant or the home owner comes to investigate the problem. While this may be quite satisfactory for instances in which the freezer or refrigerator is attended most or all of the time, such as in a home, there are many instances in which the freezer or refrigerator is left relatively unattended for hours or days at a time, in which case the self-contained power source fails or goes dead prior to the time anyone is on the scene to investigate. In such cases, when someone finally does come and the power source has failed there is no warning signal emitted. Even though the contents may still be frozen or salvagable, since no alarm is sounded, no investigation is made.